1. Field of the Invention
This invention relates to an assembly for mixing and dispensing preparations of two or more components.
2. Description of the Related Art
A number of devices have been developed which are intended to serve as a shipping, storage, mixing and dispensing container for small quantities of preparations made of two or more components. Some of these devices are particularly desirable for single-use applications such as one-patient applications in the medical and dental fields. Certain devices, for example, are used in dentistry for two-component glass ionomer cement systems that serve as adhesives, bases, liners, luting agents, sealants, and filling materials for restorative or endodontic use.
Ionomer cement systems typically are made by mixing a small quantity of glass powder with an aqueous solution of polycarboxylic acid. Representative ionomer cement systems are described in U.S. Pat. Nos. 4,872,936, 4,209,434 and 3,814,714 as well as European Patent Application Nos. 0 323 120 and 0 329 268. Dental ionomer cement systems are often characterized as having relatively short working times (e.g., on the order of one to two minutes) and as a consequence preferably are applied directly to the tooth cavity or other work site from a capsule or other small container that is used for both mixing and dispensing the cement.
Mixing and dispensing capsules for two-component dental preparations are described in U.S. Pat. Nos. 3,595,439 and 4,648,532 and U.K. Patent Application No. 2 220 914. In brief, such capsules include a hollow capsule body having an outlet on one end, a piston received in an opposite end, and a barrier within the body that initially separates the two components. When desired, the barrier is ruptured and the components are mixed by placing the capsule in an amalgamator. The capsule is then placed in a dispensing device to advance the piston and eject the mixed preparation through the outlet.
The barrier of the capsule described in U.S. Pat. No. 3,595,439 is ruptured by placing the capsule in a pressure-inducing device that together advances a cap and plunger toward a tubular body portion. After the components are mixed in an amalgamator, the capsule is placed in a receptacle of a hand extruder having a ram which is movable through a hole in the capsule cap for advancement of the plunger to dispense the preparation while the cap remains stationary.
Advantageously, the overall length of the capsule shown in U.S. Pat. No. 3,595,439 is too large to fit within the receptacle of the extruder unless the barrier has been ruptured by advancement of the cap and plunger toward the tubular body of the capsule. Such construction serves to remind the user that there are two components in the capsule that should be mixed by the amalgamator before beginning the dispensing operation.
However, the mixing and dispensing capsule described in U.S. Pat. No. 3,595,439 is used with two tools: the pressure-inducing device to rupture the barrier and "activate" the capsule, and the hand extruder for discharging the mixed preparation from the capsule. The purchase, handling and cleaning of two tools results in additional time and expense.
U.K. Patent Application No. 2 220 914 describes in one embodiment an assembly of a capsule and a single dispensing device, wherein the dispensing device is placed in a first position to rupture a barrier and then placed in a second position to eject the contents. However, there is a possibility that a ram of the dispensing device may be advanced too far when such a capsule is in its first position, resulting in unintentional discharge of the contents of the capsule before the contents have been properly mixed.